Wireless signaling system.



No. 776.337. PATBNTED 1107.29, 1904. L. MANDELSTAM & H. BRANDBS.

WIRELESS SIGNALING SYSTEM.

APPLICATION FILED SEPT. 8' 1904.

' no MODEL.

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UNiTEn STATES Patented November 29, 1904.

PATENT OEETCE.

LEONID MANDELSTAM, OF BERLIN, AND HERMANN BRANDES, OF STRASS- BURG,GERMANY.

WIRELESS SIGNALING SYSTEM.

SPECIFICATION forming part of Letters Patent No. 776,337, dated November29, 1904.

Application filed September 8 1904. Serial No. 223 7413: (No model.)

To all whom it may concern:

Be it known that we, LEONID MANDELsrAM, doctor of philosophy, a subjectof the Emperor of Russia, residing at No. 35 Joachims- 5 thalerstrasse,Berlin, Germany, and HERMANN BRANDES, a subject of the King of Prussia,Emperor of Germany, residing at Strassburg, (Physikalisches Institut derUniversitat,) Al- 'sace, Germany, have invented certain new 10 anduseful Improvements in Wireless Signaling Systems, of which thefollowing is a full, clear, and exact description, reference being hadto the accompanying drawings, forming a part of this specification.

5 This invention relates to a wireless signaling system in which thereis employed as transmitter a simple transmitter, or a so-called coupledtransmitterthat is to say, an aerial conductor in conductive orinductive connection with an eXciting-circuit-and also as receiver anaerial conductor in conjunction with a receiving-circuit containing adetector.

This invention is intended to obtain in such telegraph systems as closea tuning as possibio of the receiver to the transmitter. For this objectit has been found necessary that the receiver-circuit should be looselycoupled with the aerial conductor and also that the 3 damping of thereceiving-circuit be reduced as far as possible and the capacity of thereceiving-circuit kept as far as possible constant.

Where in the present invention a simple transmitter is employed, ofcourse no mention of a coupling is necessary; but in all cases Where bythe present invention the operation is carried out with atransmitterwhich consists of an aerial conductor and an excit- 4 ing-circuitconnected therewith it is assumed transmitter, and, further, that thiscombination while admitting a close tuning between 5 the transmittingand receiving stations must in principle have a much smaller scope thanthe combination of a firmly-coupled transmitter with an alsofirmly-coupled receiver. By the loose coupling of two vibrating systernsWieu understands a coupling in which the back action is so small thatthe coupled system in case of resonance of the two sepa ratesystems onlyshows vibrations of a single vibration period (this is similar to theselfvibration of each separate system) in contrast to a firm coupling inwhich the coupled system shows two vibrations, one of which is smallerand the other larger than the self-vibration of the uncoupled systems.The re- 5 searches of W'ien are of a purely theoretical character andtake for granted data which are also theoretically deduced.

In the specification of the present invention the theory stated by Wienis taken as 7 characteristic of the loose coupling. Now experiments haveshown that the combination of a firm coupled or a simple transmitterwith a loosely-coupled receiver not only allows of close tuning, butalso the bridging over of wide distances, assuming that the secondarysystem of the receiver is formed so as to be adapted to be closely tunedby suitable dimensioning of the constituents and by a suitable method ofswitching. In all the vibration-circuits coming in question in thetransmitter and receiver the secondary circuit of the receiver (thedetector-circuit) is characterized by its damping being merely dependenton the ohmic resistances contained in it. Now 8 5 in order to reduce asfar as possible the damping of this circuit, which is necessitated bythe Joule heat, by the present invention for making the winding aconductor is employed of non-magnetic material of good conduc- 9 tivity,the diameter of which is at least .025 inch. Hitherto a very thin wirewas usually employed for this object, about .004 inch diameter-that isto say, about six times thinner than in the present case. Instead of asolid wire a braid or lace may also be employed in the present case,whereby the losses produced by eddy-currents are also substantiallydiminished. It is also necessary in order to obtain and maintain assharp a tuning of the receiver-circuit as possible that the capacity ofthe same shall remain as far as possible constant. Now, however, thedetector which lies in the secondary receivercircuit represents acapacity which does not remain constant, but, on the contrary, is liableto alterationsfor instance, by vibration or from other causes. In orderto make these variations to have as slight an influence as possible onthe actual periods of the receiver System, by the present invention thetotal capacity of the receiver-circuit in comparison to the detectorcapacity is made atleast twice as great as the latter. Experiments haveshown that such an enlargement of the capacity as compared to thedetector capacity makes the fluctuations of the latter almostinoperative on the actual periods of the receiver-circuit. The increaseof the capacity of the receiver-circuit may be obtained either by acondenser of suitable size being inserted in parallel to the detector orby the self-induction coils contained in the receiver-circuit beingthemselves given the necessary capacity by suitable form andconstruction.

The invention will be more particularly described in connection with theaccompanying drawings, in which Figure l is a diagrammatic view of asimple transmitter. Fig. 2 is a diagrammatic view of a single receiver.Fig. 3 is a diagrammatic view of a coupled receiver. Fig. I is adiagrammatic view of a coupled transmitter.

Fig. l is a simple transmitter which acts in conjunction with thereceiver shown in Fig. 2. The latter is formed of an aerial conductor a,which is conductively but only loosely coupled with a receiver-circuitb. The loose coupling is here attained by only a portion of the totalself-induction contained in the receivercircuit, being employed forcoupling with the aerial conductor a-that is to say, in other Words,only a portion of the coil 0 of the receiver-circuit lying within theaerial conductor a. The receiver-circuit contains in addition to thiscoil 0 a coherer (Z. The selfinduction coil is by the present inventionformed of a conductor of good conductivity and having a diameter of atleast .025 inch. A condenser f is switched on in parallel to thecoherer, through which condenser the capacity of the receiver-circuit isbrought to at least twice the amount of the capacity of the coherer.Instead of loosely conductively coupling the receiver-circuit with theaerial conductor the coupling may also take place inductively, as shownin Fig. 3, the loose coupling being obtained in the ordinary manner forinstance, by leaving a space between the primary and the secondary coilsof the converteror by only a smaller portion of the selfinduction of thereceiver-circuit acting in conjunction with the primary coil of theaerial conductor.

Instead of the simple transmitter shown in Fig. 1 there may, as alreadystated, be employed one having an eXciting-circuitthat is to say. acoupled transmitter, as shown in Fig. 4.. The exciting-circuit may thenbe induetivel y connected with the aerial conductor, as here shown, oreven conductively connected while as firm a coupling as possible isdesirable. i

It is easily evident that the effectiveness of the receiver systemhereinbefore described is affected by the size of the spark-gap of thetransmitter, inasmuch as the damping of the latter increases with anenlargement of said spark-gap. It has therefore been found preferablefor the combined action with the receiver system described in all thecases where the spark-gap exceeds a certain size to employ instead ofone large one several small onesthat is to say, to divide thespark-gaps, as shown in Fig. 4:. In order in this case to obtain auniform distribution of the potential charge over the separatespark-gaps, it is necessary to arrange potential-distributers parallelto the separate spark-gaps, which potential-distributers are of lessconductivity for the rapid discharge vibrations. As means fordistribution of potential very small condensers, self-induction coils,and high ohmic resistance have been found effective. It is easily seenthat such a division of the sparkgaps may also be employed with likesuccess in the sample transmitter shown in Fig. 1.

The following have been found to be the most favorable methods oftuning, the number t M represent the self-vibration of theexcitingcircuit and the aerial conductor separated from one another, andM and M the two partial waves of the coupled circuit. In a simple or afirmly-coupled transmitter with receivercircuit, the coupling degree ofwhich does not exceed a given value, which lies between fifteen percent. and thirty per cent, the most favorable action is obtained if bothcircuits of the loosely-coupled receiver be tuned to the self-vibrationsof theloosely-coupled transmitter. If a coupled transmitter be coupledfirmer than that stated, the tuning is onto a length of wave moreclearly approaching the short wave. In still firmer coupling of thecoupled transmitter the receiver is preferably tuned to the short wave.For tuning the detector-circuit it is advisable to vary theselfinduction of the coil contained in this circuit. In this case thedevice for varying the selfinduction can be provided with an indicatorshowing on a scale the periods or wave lengths of the detector-circuitwhich correspond to the actual alterations (or variations) of theselfinduction.

being defined as degree of coupling if Having explained our invention,what We do claim, and desire to secure by Letters Patent, 1s-

1. In a wireless signaling system the arrangement of a transmitter and areceiver, the receiving-circuit of which is loosely coupled with theaerial conductor and a detector and a self-induction coil within thereceiver-circuit, the capacity of the latter being at least twice aslarge as the capacity of the detector with the object of diminishing thefluctuations of the capacity caused by the detector substantially asdescribed.

2. In a wireless signaling system the arrangement of a transmitter and areceiver, the receiving-circuit of which is loosely coupled with theaerial conductor and a detector and a self-induction coil Within thereceiver-circuit, the self-induction being formed of a conductor of goodconductivity and a diameter of at least .025 inch, in order to diminishas far as possible the damping in the receiver-circuit substantially asdescribed.

3. In a wireless signaling system the arrangement of a transmitter andreceiver, the receiver-circuit of which is loosely coupled with theaerial conductor, and a detector and a self-induction coil within thereceiver-cir cuit, the self-induction coil being formed of a conductorof good conductivity and a diameter of at least .025 inch, the capacityof the receiver-circuit being at least twice as great as the capacity ofthe detector substantially as described.

4C. In a wirelesssignaling system the arrangement of a transmitter inconjunction with a divided spark-gap within the aerial.

conductor or in an exciting-circuit firmly coupled with the latter, areceiver, the receiving-circuit of which is loosely coupled with theaerialconductor and a detector and a selfinduction coil within thereceiver-circuit, the capacity of the receiver-circuit being at leasttwice as great as that of the detector substantially as described. 1

5. In a wireless signaling system the arrangement of a transmitterconductively or inductively connected with an exciting-circuit, areceiver, the receiving-circuit of which is more loosely coupled withthe aerial conductor than the exciting-circuit with the aerialconductor, a detector and a self-induction coil within thereceiver-circuit the capacity of which is at least twice as great asthat of the detector substantially as described.

6. In a wireless signaling system the arrangement of a transmitter and areceiver,

the receiving-circuit of which is loosely coupled with an aerialconductor, and a detector and a self-induction coil within thereceivercircuit. the latter being formed of a conductor of goodconductivity and of a diameter of at least .025 inch, and thearrangement of a condenser of suificient capacity parallel to thedetector for diminishing the fluctuations of the capacity caused by thedetector substantially as described.

7. In a wireless signaling system' the arrangement of a transmitter anda receiver, the receiving-circuit of which is loosely coupled with theaerial conductor, and a detector and a self-induction coil within thereceivingcircuit, the latter formed of a conductor of good conductivityand of a diameter of at least .025 inch, and having a capacity which isat least twice as great as that of the detector substantially asdescribed.

8. In a wireless signaling system the arrangement of a transmitter incombination with a divided spark-gap, means of lesser conductivity forthe rapid discharge vibrations parallel to the separate spark-gaps, areceiver, the receiving-circuit of which is loosely coupled with theaerial conductor, a detector and a self-induction coil within thereceiver-circuit, the capacity of the latter being at least twice asgreat as that of the detector, and the selfinduction coil being formedof a conductor of at least.025 inch diameter substantially as described.

9. In a wireless signaling system the arrangement of a transmitter and areceiver, the receiving-circuit of which is loosely coupled with theaerial conductor, a detector and a self-induction coil within thereceiver-circuit, the self-induction coil being formed of a conductor ofat least .025 inch diameter, means for altering the self-induction ofthe coil and means for inducting the Wave lengths or periods of thevibrations of the receiver-circuit which correspond to the actualalterations (or variations) of the self-induction substantially asdescribed.

In witness whereof we hereunto subscribe our names this 23d day ofAugust, A. D. 190%.

LEONID MANDELSTAM. HERM. BRANDES. Witnesses:

HENRY HAsrnn, WOLDEMAR HAUPT.

